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  1. #1
    Fat-tired Roadie
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    Existing SUV - maximizing fuel efficiency

    I just got a new job and will now be commuting on the freeway quite a lot. Maybe as much as 30,000 miles/year, depending on whether or not I can find a carpool or telecommute some days or something.

    When I bought my SUV, I was riding my bike to school and really only used the truck it replaced to go mountain biking, go skiing, go to races, etc. So a car that doesn't need chains in the snow most of the time and has room for bikes and skis inside was a great fit for me.

    Having played with some numbers, the utility of buying a new car to get better gas mileage seems pretty dubious to me. But I wonder if I can improve the fuel efficiency of what I have (2000 Nissan Pathfinder) a bit.

    I've already removed the cross bars for the roof rack. It doesn't appear to have made much of a difference; certainly not enough to detect past the inconsistency in how far up the fuel pipe different gas pumps seem to pump. I'm probably still going to get rid of the wind deflectors, though I anticipate that will make even less difference. It doesn't have any silliness like guards over the lights.

    It has crossed my mind that using freeway tires in the summer might help. Currently the car has the usual M+S tires that SUVs and light trucks tend to come with. Even Consumer Reports found that high-efficiency tires really do improve efficiency, and they're pretty conservative.

    Other ideas I had were things like getting the car lowered and a chin spoiler and skirts. But these seem likely to be relatively expensive, and the idea here is to try to make it cost less. Although even a 1 mpg improvement is worth close to $400. (So the tires are almost a no-brainer, but I think suspension work involving aftermarket parts is expensive.)
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  2. #2
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    Tires are a good idea, make sure they are always well inflated.
    Don't bother with chin spoiler/skirts, they won't help much. Look into ways to smooth the air transition under the car, so maybe a skid plate.
    Also, make sure the car has a good alignment, no need to waste money dragging tires sideways.


    You've probably already seen this list, but it does have some pretty good suggestions (specially about the spark plugs/air filter)

    Ways to Improve Fuel Economy : Nissan Articles

    The best advice that page gives is to change the way you drive, become that annoying driver going 55, fuel economy drops off exponentially once you get above 55-65 mph.

  3. #3
    Fat-tired Roadie
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    I hadn't seen that article, actually. I'm not really a car person, haven't even owned them for good chunks of my adult life. So maintaining them myself and driving them other than stock haven't really been things I've thought about in the past.

    A lot of the stuff in the article sounds like it could be part of my tuneup, maybe for an upcharge.

    The underbody stuff sounds interesting. I've been under my car a little bit, and there's all sorts of stuff sticking out down there. So probably some real room for improvement.

    Hopefully I'll be able to carpool or something. But I'm bookmarking the link so if I end up commuting every day, I can mitigate some of the burning money. From reading that and the discussion of alignment, it sounds like my first stops should be a good tuneup and some more efficient tires - I can get the alignment looked at at the same time.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  4. #4
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    Low Rolling Resistance Tires can make a difference.

    Tire Search Results

  5. #5
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    Spark Plugs
    Air Filter
    Synthetic oil
    Fuel injector cleaner
    New transmission fluid, diff fluid, transfer case fluid (if 4x4).

    Clean your Mass Air Flow sensor.

    If your Pathfinder is a 4x4, warn locking hubs can add a MPG or two. When driving in 2WD mode, the front wheels spin the front axles, which spins the front differential, which spins the front driveshaft and part of the transfer case...When you put freewheeling hubs on, these things no longer spin with the wheels, less drag. But you have to manually lock the hubs when you want 4wd (easy).

    I drive a 01 QX4 (3.5L VQ35DE) pretty much the same components except the engine difference (3.3L).

    Take off the sidesteps, they are heavy and useless.

  6. #6
    Rohloff
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    Hypermiling.

  7. #7
    Fat-tired Roadie
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    My Pathfinder is a 4x4, but it's front-wheel-drive when it's in 2WD mode. From some clicking around, it sounds like people are using locking hubs on Pathfinders of the same age as mine. I'll have to have a look at the manual and maybe a talk with my mechanic - with how frequently I use (let alone need) 4WD, that sounds like a great way to pick up a couple mpg.

    I already don't have the stupid side step. So at least I'm ahead there. I think the silly wind deflectors are the only non-integral stuff I still have stuck to the outside of my car. If I'm doing the other tires anyway, I'm starting to visualize a bit of a mode switch - big honkin' M+S tires during the ski season and smoother touring tires and freewheeling hubs the rest of the time. I do like my car, so if I can narrow the efficiency gap some during most of the year, it would be nice.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  8. #8
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    It's rear wheel drive

  9. #9
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    make sure you have correct tire pressure, for the maximum economy air pressure should go as high as tires allow but I wouldn't go at the max probably door sticker recommended pressure plus 2-3 psi would be good. for P-rated tires of course.

  10. #10
    Mtn View, CA
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    Just get a used econobox for $1k or less like a Corolla or Civic. 30mpg easy. It'll be paid off quick on just gas use.
    Otherwise, lighten up the Pathfinder as much as possible. Proper tire pressure. Coast to a stop.
    Atomic batteries to power...turbines to speed...

  11. #11
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    You could always glass up a Kammback or boat tail for it:

    Transition Bandit 29
    Surly Ogre
    Surly Necro Pugs w/ Lefty PBR
    Surly Big Dummy

  12. #12
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    Quote Originally Posted by gddyap View Post
    Just get a used econobox for $1k or less like a Corolla or Civic. 30mpg easy. It'll be paid off quick on just gas use.
    Otherwise, lighten up the Pathfinder as much as possible. Proper tire pressure. Coast to a stop.
    +1. You can pay for a used econo-car pretty quickly in gas savings.

  13. #13
    Fat-tired Roadie
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    Quote Originally Posted by nnorton44 View Post
    It's rear wheel drive
    I wonder why I thought it was front. Anyway, that would explain why it develops under steer when I put it in 4.

    I don't think I know cars well enough to get good COO out of a $1000 car. Anyway, that version of the plan would be to drive my fiancee's little Kia. I may end up doing that, but I like my car.

    I had a chance to clock my trip up today, partially along my commute route, and only 25 miles of it actually have a 70 mph speed limit. So I think I'll quit setting "cruise" higher for those sections - it's saving me maybe 3 minutes, and I know my car is operating fairly inefficiently by 80.

    The Kamm Back had crossed my mind... It would go well with getting rid of all that extra crap in my exhaust system. I don't think I even need it to register my car in my new county, so I may as well be getting some money for the platinum in the catallytic converter.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  14. #14
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    its a boring answer, but your behavior in the car can often have much more impact on mileage than the car itself. avoid driving with the windows down, using (or i guess overusing) the AC, heater, radio, heated seats, daytime headlights, whatever else the car is using electricity for... use the brake pedal as a gauge for the quality of your "hypermile" driving. the less you use the brake pedal, and the shallower you press the gas pedal, the better you should be doing. draft trucks (closely, if you dare). get an app like gasbuddy on your phone to help you locate the best local gas prices, and do your best to avoid traffic (maybe leave early in the morning and in the evening too)

    as far as the machine, get an alignment with the minimum toe allowed by the manufacturer's specifications (or if you like, get an alignment with literally zero toe... the car will handle a little funny on the highway though). empty the car of everything you don't need to have with you. turn the car off when standing for prolonged times. as others have said, keep tire pressures at maximum allowable, and consider tires with less rolling resistance than your m&s. keep your oil changed regularly. make sure your air filter is new/clean.

  15. #15
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    Please leave your catalytic converter in place, unless it's clogged removing it won't gain you any more mileage.

  16. #16
    Captain Climber
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    Something I learned from bobistheoilguy.com was to add a few ounces of 2 stroke outboard oil to the gas tank when I filled up. I actually improved my Xterra's average MPG from 19 to 21-22. It's been a while since I have done this because I ride to work now and seldom drive. Check there for the details of how much to add per gallon and the type of oil to use.

  17. #17
    Elitest thrill junkie
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    Quote Originally Posted by AndrwSwitch View Post
    I had a chance to clock my trip up today, partially along my commute route, and only 25 miles of it actually have a 70 mph speed limit. So I think I'll quit setting "cruise" higher for those sections - it's saving me maybe 3 minutes, and I know my car is operating fairly inefficiently by 80.
    God yes. I went across the country (South to North) in my V8 2011 Camaro last year and squeeked out 25-26mpg (25.9 if I remember right). That ain't "good mileage", but for that car, it's damn good. How? Don't go more than 5mph over any speed limit, even choose to go the actual speed limit at times, I wasn't aggressively hypermiling, but by doing that I can squeek out more like 28, just not worth it for me though. Pretty big difference in mileage from 70 to 80. I enjoy going fast as much as the next person and at certain times in certain situations I do, but it's easy to waste a lot of gas too. If you have a manual, you get more control over this can can avoid using the brakes more. Skipping shifts saves gas, with my engine I can go right from 1 to 4, and from 4 to 6, heck, I can go from 1 to 6 if I want, but that gets a little ridiculous. On my car, they did the 1-4 shift skip and a very high geared 6th, so the engine turns over very low RPMs in top gear. A torquey engine helps, but if you got the 6cyl, I'm sure it would work to go from 1 to 3 and 3 to 5.

    Change your habits, you'll see the most improvement IMO, not huge, but noticeable IMO.

    Things that don't work?

    Cutting your exhaust
    Additives
    Cold air intakes
    Etc...
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  18. #18
    ballbuster
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    Quote Originally Posted by scanny View Post
    make sure you have correct tire pressure, for the maximum economy air pressure should go as high as tires allow but I wouldn't go at the max probably door sticker recommended pressure plus 2-3 psi would be good. for P-rated tires of course.
    .... Unless you wear the center of your tires out. If you're only getting half the tire's life because they are wearing out prematurely, that will probably cancel any money you saved on gas. I did this with my Audi A4, and kinda regretted it. The tires wore out early, and started making Wubba Wubba Wubba noises. I thought it was the front wheel bearings, so I changed those out unnecessarily (did it myself to the tune of $75 each, so no big expense apart from my time). But, I did end up having to change out a set of $700 tires prematurely. There was only a slight increase in fuel efficiency.

    As long as you aren't under inflating your tires, there isn't much fuel to be saved by overinflating, at least in my experience.

    You can also try running the timing a bit more advanced, if you car's ignition system lets you do that. Just don't advance it so much it pings.

    There isn't much lost in the electrical system, but it couldn't hurt, I guess. I mean, really.... 1 Horsepower = 745.7 watts. I don't think turning off your 10 watt stereo is going to yield a difference you will ever see. I guess your headlights are 65W each on high beam. Granted, an alternator isn't converting 100% of the energy sucked from the engine into electrical power, but... Meh...

    Yeah, if you're driving a manual, then try short shifting. Get the car rolling, go to second gear, and accellerate the car at full throttle but control the speed with your shift points. The engine is most efficient at full throttle because it isn't drawing a vacuum. If you wind the engine out, it sucks a ton of gas, but if you shift when you get to the point where the next gear can turn without lugging, then you take as much advantage of this lack of manifold vacuum as much as possible.
    Last edited by pimpbot; 04-03-2013 at 09:36 PM.

  19. #19
    Fat-tired Roadie
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    It's an automatic. So some power loss there and not much opportunity to make choices about my shifts. I live in WA and people in this state can't drive. It's not much, I know, but I'm supposed to be a bit safer leaving my headlights on full-time.

    For tires, I've read some contradictory stuff about pressure. Including here, now. If I end up driving the commute every day, more appropriate tires are definitely one of my action items. I'll probably just follow the manufacturer's recomendation on pressure at that point. If it's the same as the pressure I'm using right now, Nissan's recommended, I'll revisit the issue - I think it's a little low, for better traction on dirt, which is a compromise I'll be less interested in if I'm driving so much more on the freeway.

    As far as driving habits, this is about a 60 mile commute with about 50, maybe even 55, on the freeway. I spend a ton of time in cruise control. For the next little while, I'm just going to quit going over 70. When I've been at my job long enough to see if I can carpool, if that's not feasible, and I hate my fiancee's Kia, I'm going to look at tires and locking hubs.

    Removing the catallytic converter isn't something I'd really do, but I have noticed that my previous car and this one were both more efficient with damaged exhaust systems. Lots of holes in the pipe and muffler on my old Ranger, and this one had sheared at the flange between the muffler and resonator. Getting them fixed cost me a mile or two in both cases. No surprise, really, but it certainly makes an otherwise blaise person wonder about aftermarket exhausts.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  20. #20
    jrm
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    What about changing modes? that would help. Is there transit available? could you ride and then take a bus/train the remainder of the commute?

  21. #21
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    There is nothing contradictory with tires pressure, it's all simply physics. The more contact your tires have with pavement the more rolling resistance you have and engine has to use more power (i.e. gas) to keep vehicle rolling. I agree with pimpbot above that is tire pressure is too high you will wear them in the centre but I don't think 2 psi over sticker recommended is going to hurt. But anyway if you're under recommended pressure it hurts fuel consumption for sure. And be aware that tire pressure will change with temperature, so check it at least once a month. Also heavier tires are less fuel efficient, so if you are to buy new tires, check their weight and try to buy tires not heavier than you have now.

  22. #22
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    Grab a K&N air filter. They're cheap, flow better than stock, clean better than stock, and will last longer than the rest of the car. Good for 5-10HP if you're worried about speed, or a few MPG if you're staying off the gas.

    If you're driving gingerly, you can get away with running lower octane gas as well, not sure if your car requires mid or premium. Keep the AC off, use cruise control, drive slower, accelerate slower. Brake early and try to time redlights to coast through them as soon as they turn green.

  23. #23
    Fat-tired Roadie
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    My time is worth something to me, and there's no income tax in this state. So public transit's out. Plan A, if it works out, would be to find a carpool.

    I really hate it when people say something is "simply physics." Theoretical models are okay for gaining some insight, but once things are as similar and down to differences as small as efficiency at +/- 2 psi, and do contain contradictions - I was referring to the idea that wearing out the center tread too fast kills a tire early, eliminating my savings contradicting the idea of running at a few extra psi - IME it takes an empirical model to say anything in reality. Including whether or not a theoretical model is even valid. Another problem with the extra pressure idea is that it does make the car tend to move up and down more, and the energy to move the car up against gravity has to come from somewhere. That's not to say I'm not going to look at it, though I suspect I may get a good pressure recommendation alongside a set of freeway tires. Just that you can't pull a half-understood theoretical model out of your ass and claim it's the truth.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  24. #24
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    Tire pressures as well as driving style.

    40 psi is a good idea. I did that on Jeep Cherokee with aggressive BFG All terrains and was worht 1 mpg. I could get 19mpg on my commute. I when to 17 mpg with a 4" lift and roof rack and 31" tires. I estimate 1 mph from the rack and 1 mpg from the lift/tires size. (I corrected the speedo so that was not an issue). 40 psi never caused me any wear problems as SUV are heavy and most run low pressures for "comfort".

    Driving style is going to be big one though. The best thing to do is slow starts. Meaning 0-60 in 30 seconds rather than punching it. On the highway stick to the speed limit and draft cars when possible. Not close as to dangerous, but run in-line vs side by side. And also consider driving with momentum like you would on the bike. Meaning more gradual starts and stops.

    This might get you to 20 mpg on the highway, but that is going to be about all you can do unless you do something radical which may never pay off.

    My wife has SUV 6cylinder that gets high teens low 20's for MPG. This was fine when she was a stay at home mom, but now she has to drive out 6 year old to school. It is 20 miles one way and she has to do that trip upto 4 times a day. I drive a car on my 38 mile one way commute and get 28 mpg. Running the numbers it only cost about $1000 more a year at 20 mpg vs 28 mph. Even moving to a 40mpg diesel car will only bring $2000 a year in fuel savings.

    My point is spending $2000 to save $1000 in fuel a year is kind of tough. Now when my wifes SUV does need to be replaced due to age/miles we will try to find something closer 28 mpg as we are going to spend the money anyway.

    Now one big relief is that we found carpool with another family. My wife does mornings and they do afternoons. So effectively her mileage is from 19 mpg to 38 mpg and less wear on the car too!
    Joe
    2003 KHS Alite 4000 26" Hardtail - XC, All mountain, blah blah blah.. I just ride.

  25. #25
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    Quote Originally Posted by nnorton44 View Post
    Spark Plugs
    Air Filter
    Synthetic oil
    Fuel injector cleaner
    New transmission fluid, diff fluid, transfer case fluid (if 4x4).

    Clean your Mass Air Flow sensor.
    ...
    Yeah, but all this only helps get back to rated mileage when new. It will not get you beyond that. If motor is not working properly it should be fixed.
    Joe
    2003 KHS Alite 4000 26" Hardtail - XC, All mountain, blah blah blah.. I just ride.

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